The present invention pertains in general to fuze actuating systems and in particular to fuze actuating systems comprising a timer having a variable impact delay.
In the design of projectile fuzes for impact function it is often desirable to provide for detonation of the projectile within the target, such as an aircraft structure, rather than at the instant of first contact with the target. This can be accomplished in myriad ways, ranging from a simple non-varying delay time between first impact and detonation to a delay time that is dependent upon the dynamics and geometry of projectile approach to and interaction with the target. As the degree of fuzing elegance increases, the production cost of fuze hardware generally increases also.
The time of detonation delay may be varied as a function of projectile flight time to the target. Because the latter is a known function of projectile velocity, detonation delay becomes a function of projectile velocity at target impact. In turn, the depth to which a projectile invades the target media before detonating can be controlled within reasonable bounds by increasing the detonation delay time of the fuze as range to the target increases.
The invention is particularly suited for use in fuzes for "fixed" ammunition in the direct fire mode. For example, the technology of this invention is amenable to ammunition for modern anti-aircraft gun systems in the size range 25 to 40 mm. Both nose mounted and base mounted fuzes can use the technique to enhance the performance of the ammunition.
In one approach to providing impact delays in electronic fuzes, as illustrated by U.S. Pat. No. 4,240,350, issued to K. Munzel, P. Karayannis and H. Naef, a fixed delay is provided by means of an arrangement of logic gates. However, the timer used in this approach requires two oscillators, one for barrel safety and one for the impact delay, and yet only provides a fixed impact delay. Therefore this approach does not allow optimal target penetration.
In yet another approach to providing electronic impact delays, a variable delay of U.S. Pat. No. 4,320,704, issued to H. Gawlick, U. Brede, and H. Bendler, is implemented by charging a capacitor to a degree determined by the flight time of a projectile as an integration of flight time and then discharging the capacitor through a resistance after impact in order to provide a delay related to flight time before detonation. However, an extremely steady current source is required for such an impact delay system to be accurate. Meeting the sorts of tolerances required is extremely difficult in a mass-produced fuze. Furthermore, such a fuze is not readily programmable.